Dental prosthetic appliance



28, 1959 R. w. CHRISTENSEN v 3, 7

DENTAL PROS'I'HE'I'IC APPLIANCE Filed Oct. 19, 1965 I N VE N TOR.fmierh/ [QR/175m Arm/mm W 2 was United States Patent 3,474,537 DENTALPROSTHETIC APPLIANCE Robert W. Qhristensen, Palos Verdes Estates, Calif.(175 S. El Molino, Pasadena, Calif. 91106) Filed Oct. 19, 1965, Ser. No.497,623 Int. Cl. A61c 13/22 11.5. Cl. 32-10 4 Claims ABSTRAQT OF THEDISCLOSURE An anchor post adapted to be threaded vertically through alower jawbone to provide a stable mounting for a denture or artificialtooth. The post has an enlarged head which fits against the underside ofthe jawbone, and one or more small locking screws extended obliquelythrough the head into the jawbone to lock the shaft against rotation.The upper end of the post extends above the jawbone and gum tissue forengagement with the denture or artificial tooth.

BACKGROUND OF THE INVENTION When natural teeth must be replaced, animportant goal is to provide a firm anchor or mounting for antificialtooth or for a denture comprising several artificial teeth. Achievementof this goal helps to assure patient comfort and to permit normalchewing. Further, disintegration of the alveolar ridge of the jawbonewhich may occur with a loose, poorly secured denture, is avoided whenthe denture is firmly anchored.

In the past, some dentures have simply been fitted to the patients gumstructure without any positive anchoring. This often results in a loosedenture which prevents normal chewing. Another approach is to use apermanent bridge assembly which is secured by inlays secured toadjoining natural teeth. This method provides a relatively securemounting, but requires removal of portions of the natural teeth, and maypose hygienic problems as well as making X-ray examination moredifiicult.

Still another approach to anchoring artificial teeth is to implant asupporting structure within the gingival or gum tissue and restingagainst or around the jawbone. Several techniques utilizing thisappproaeh are described in my U.S. Patent No. 3,082,525 issued Mar. 26,1963, and entitled Dental Prosthetic Appliance. This earlier patentdescribes an improved subperiosteal implant which is secured around thejawbone and provides a mounting post or stud which extends through thegingival tissue to engage and anchor a denture.

My present invention relates to an improved implantable prostheticappliance which is secured in a hole drilled through the mandible orlower jawbone. The device extends from the jawbone through the overlyinggingival tissue to provide an intra-oral mounting post for an artificialtooth or denture.

The invention is a substantial improvement over known implantabledevices in that a relatively simple surgery is involved, and a strongdenture mounting is provided as the device is firmly secured in thestrongest part of the jawbone. Only two relatively small areas of tissueneed be separated from the jawbone, promoting rapid healing and greaterpatient comfort. Another advantage of the invention is that theimplanted appliance is quite small, and pockets or traps for bacteriaare minimized, reducing the danger of spreading infection.

Briefly stated, this invention relates to a dental prosthetic appliancefor implantation in a jawbone and overlying gingival tissue. Theinvention comprises an elongated shaft of implantable material. Theshaft has a flattened head integrally formed and extending laterallyfrom one end thereof. The end of the shaft opposite the flattened3,474,537 Patented Oct. 28, 1969 ice head forms a mounting post adaptedto engage a denture. An intermediate portion of the shaft between theflattened head and the mounting post is adapted to be secured within thejawbone. The shaft is dimensioned whereby the mounting post extendsbeyond the gingival tissue overlying the jawbone into the oral cavity ofthe patient.

In a preferred form of the invention, the intermediate portion of theshaft includes self-tapping threads to secure the shaft within thejawbone. Preferably, the flattened head includes at least one holetherethrough, the axis of this hole being oblique to the axis of theelongated shaft. An implant screw is inserted through this hole into thejawbone, providing secondary anchoring of the appliance and preventingundesired rotation of the shaft within the jawbone.

The invention will be described in detail with reference to the attacheddrawings in which:

FIG. 1 is an elevation of the prosthetic appliance of this invention;

FIG. 2 is an end view of the appliance, showing a plurality of holes inthe flattened head;

FIG. 3 is a fragmentary elevation of an alternative form of theinvention, showing a mounting post having threads to engage a denture;

FIG. 4 is an elevation of a lower jawbone, showing a pair of prostheticappliances of the invention installed in the jawbone; and

FIG. 5 is a perspective view of a screwdriver adapter used to installthe appliance in the jawbone.

Referring to FIGS. 1 and 2, a prosthetic appliance 10 includes anelongated shaft 11 of an implantable material. A flattened head 12 isintegrally formed at one end of the shaft, and extends laterally awayfrom the shaft.

An intermediate portion of the shaft includes threads 14 to secure theshaft within the jawbone. Preferably, the threads are of aself-threading type, and have a relatively broad root 15 whereby theamount of bone confined between individual threads is maximized.

The end of the shaft opposite flattened head 12 forms a mounting post 17to engage a denture. The portion of the shaft extending from thethreaded intermediate portion to the end of the mounting post has adiameter no larger than the minor diameter of the threads whereby thisportion of the appliance can be inserted into a pilot holev drilledthrough the jawbone.

The flattened head of the appliance may include a slot to engage aconventional screw-driver. In a preferred form of the invention, thehead includes a plurality of holes 19, the axes of which are obliquelyoriented to the longitudinal axis of the shaft. When the appliance isscrewed in place in the jawbone, one or more implant screws 21 areinserted in holes 19 and threaded into the jawbone. The appliance isthereby even more firmly anchored within the jawbone, and the implantscrews resist any rotational forces on the mounting post tending tounscrew the appliance.

The appliance is dimensioned whereby the threaded intermediate portionof the shaft is confined substantially within the jawbone. Mounting post17 extends above the jawbone and overlying gingival tissue to extendinto the oral cavity. The mounting post may have a smooth surface towhich an artificial tooth or denture may be cemented. In another formillustrated in FIG. 3, the mounting post may be provided with threads 23for securing an artificial tooth or denture to the appliance. Of course,the mounting post may be necked down in diameter or otherwise formed toengage a specific type of artificial tooth or denture.

FIG. 4 shows a pair of prosthetic appliances according to the inventioninstalled in a jawbone 26, and an artificial tooth 27 (shown in phantom)is mounted on one of the appliances. To avoid interference with thenerves and blood vessels extending through the mandibular canals oneither side of the jawbone, the appliances are preferably mountedbetween left and right mental foramina 28 which mark the frontaltermination of the canals.

FIG. 5 shows a screwdriver adapter 31 which permits a conventionalscrewdriver to be used for installing the prosethetic appliance. Theadapter includes a body 32 having a front surface 33 from which extend aplurality of posts 35. The posts are spaced to engage holes 19 in theflattened head of the prosethetic appliance. The adapter includes a slot36 extending through the body. A conventional screwdriver may beinserted from the back of the body to engage the slot. Posts 35 are thenengaged with holes 19 on the appliance, and the appliance is rotated tobe threaded into the jawbone.

To install the prosthetic appliance of this invention, a sub-mandibularincision is made to expose a small area on the bottom of the lowerjawbone. A hole is then drilled upwardly through the jawbone tointercept a second small incision through the gingival tissue overlyingthe upper portion of the jawbone. The appliance is then inserted in thepilot hole and rotated whereby self-tapping threads 14 cut threads intothe jawbone. When the appliance is seated in the desired position, itmay be locked in place by inserting implant screws 21 through holes 19into the jawbone.

A feature of the invention is that the appliance is threaded through thestrong cortical portion of the jawbone and does not depend on thespongy, medullary portion of the bone for mounting rigidity. This methodof securing the appliance to the jawbone provides a wobblefree mountingfor an artificial tooth or denture, and minimizes installation surgery,patient discomfort, and healing time.

The prosethetic appliance of this invention may be formed from a metalsuch as titanium, zicronium or tantalum, or may be formed from surgicalsteel or other alloys which have been found to be suitable forimplantation in the body. In a preferred form, the invention isfabricated from Vitallium which is an alloy of cobalt, chromium andmolybdenum.

I claim:

1. In combination with an artificial tooth to be secured to a lowerjawbone and overlying gingival tissue, an anchoring post comprising anintegral shaft adapted to extend vertically through a jawbone and formedof an implantable material, the shaft having an enlarged flattened headextending laterally from a lower end thereof to abut the underside ofthe jawbone, the shaft having an intermediate portion definingbroad-root threads for direct contact with the jawbone to provideanchorage against forces tending to loosen the post, the intermediateportion being of a length approximately coextensive with the jawbonethrough which it is adapted to vertically extend, the shaft furtherhaving an upper portion adapted to extend above the jawbone and beingsecured within the tooth, the upper portion terminating within thetooth, the upper portion having a cross section which is no larger thana minor diameter of the broad-root threads on the intermediate portion.

2. The combination defined in claim 1, and further comprising meansengaged with the shaft head and adapted to contact the underside of thejawbone for providing secondary anchoring of the shaft to the jawbonewhereby rotation of the shaft is prevented.

3. The combination defined in claim 1 in which the enlarged flattenedhead at the underside of the jawbone has a hole therethrough, andfurther comprising an implant screw formed of an implantable materialand extending through the hole and engageable with the jawbone toprovide secondary anchoring of the shaft against rotation with respectto the jawbone.

4. The combination defined in claim 1 in which the enlarged flattenedhead at the underside of the jawbone has a plurality of spaced-apartholes therethrough, the holes having axes which are oblique to alongitudinal axis of the shaft and diverging from the shaft, and furthercomprising a plurality of implant screws extending. through the holes toengage the jawbone, the implant screws being positioned generally on therespective hole axis whereby the screws extend through the head withoutpenetrating the intermediate portion of the shaft.

References Cited UNITED STATES PATENTS 804,030 11/ 1905 Ostrander.

928,997 7/ 1909 Muller 151-68 2,467,163 4/ 1949 Skinner 32-2 FOREIGNPATENTS 1,320,212 1/ 1963 France.

49,639 1/ 1889 Germany. 325,203 3/ 1935 Italy.

ROBERT PESHOCK, Primary Examiner

